EP0550912A2 - Use of a voltage controlled crystal oscillator in the base unit of a two-handset cordless telephone system - Google Patents
Use of a voltage controlled crystal oscillator in the base unit of a two-handset cordless telephone system Download PDFInfo
- Publication number
- EP0550912A2 EP0550912A2 EP92122128A EP92122128A EP0550912A2 EP 0550912 A2 EP0550912 A2 EP 0550912A2 EP 92122128 A EP92122128 A EP 92122128A EP 92122128 A EP92122128 A EP 92122128A EP 0550912 A2 EP0550912 A2 EP 0550912A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- base unit
- frequency
- cordless telephone
- voltage controlled
- controlled crystal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/403—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/72—Mobile telephones; Cordless telephones, i.e. devices for establishing wireless links to base stations without route selection
- H04M1/725—Cordless telephones
- H04M1/72502—Cordless telephones with one base station connected to a single line
Definitions
- This invention concerns the field of cordless telephone instruments.
- Cordless telephone instruments for use in the home are widely available.
- Such systems comprise a base unit and a remote handunit.
- the base unit is coupled to the telephone line and communicates with the remote handunit via FM radio signals.
- a cordless telephone system a user can remove the handunit from its cradle and carry it with him a short distance from his house yet still be able to make and receive telephone calls.
- Such a cordless telephone set is known from GE cordless telephone model number 2-9675 manufactured by Thomson Consumer Electronics, Inc. Indianapolis, Indiana.
- a copending patent application bearing attorney docket number RCA 86,682 discloses a cordless telephone system which comprises a base unit and two handunits.
- a base unit transmits simultaneously to both handunits via two transmitter channels coupled to the same antenna, but during development of that system it was discovered that phase-locked loop (PLL) up-conversion used in the above-mentioned GE cordless telephone model number 2-9675 caused unacceptable intermodulation distortion in the transmitter signal from the base unit when the outputs of the transmitters were coupled together.
- PLL phase-locked loop
- VCXOs voltage controlled crystal oscillators
- PLLs frequency tripler circuitry
- FIGURE 1 is a block diagram of a cordless telephone system according to the subject invention.
- FIGURE 2 is a more detailed block diagram of the base unit of FIGURE 1.
- FIGURE 3 shows representations of the transmitter spectrum observed for both PLL and VCXO operation.
- FIGURE 1 is a simplified illustration of a cordless telephone set comprising a first handset unit 100, a second handset unit 150, and a base unit 120. Because handset units 100 and 150 are identical (except for frequency allocation), only handset 100 will be described. Handset unit 100 receives and transmits RF signals via an antenna 102. Antenna 102 is coupled to a duplex radio transceiver unit 104 which is capable of operation in a receiver mode and in a transmitter mode. In the receiver mode, transceiver unit 104 applies received and demodulated audio signals to an audio processor unit 106 for amplification and ultimate reproduction in speaker 108.
- a duplex radio transceiver unit 104 which is capable of operation in a receiver mode and in a transmitter mode. In the receiver mode, transceiver unit 104 applies received and demodulated audio signals to an audio processor unit 106 for amplification and ultimate reproduction in speaker 108.
- transceiver 104 also provides digital data to the "receive data" (i.e., Rxdata) terminal of controller 112
- transceiver 104 receives audio signals, picked-up (i.e., detected) by microphone 110 and amplified by audio processor unit 106, for transmission to base unit 120.
- transceiver 104 receives "transmit data" (i.e., Txdata) from controller 112, for transmission to base unit 120.
- Controller 112 is coupled to a keyboard 114 for receiving keystroke commands from a user.
- Handunit 100 also includes a power supply and charging unit 116 for supplying operating power to the circuitry of the handunit.
- Base unit 120 receives and transmits RF signals via an antenna 122 to remote handunits 100 and 150.
- Antenna 122 is coupled to a duplex dual radio transceiver unit 124 which is capable of operation in a receiver mode and in a transmitter mode.
- transceiver unit 124 receives RF signals at two different frequencies from remote handunits 100 and 150 respectively, and applies received and demodulated audio signals to an audio processor unit 126 for amplification and coupling to the telephone system via a telephone interface unit 128.
- Telephone interface unit 128 is connected to the telephone system via two terminals traditionally known as tip (T) and ring (R).
- transceiver 124 also provides digital data to the "receive data" (i.e., Rxdata) terminal of controller 132.
- Controller 132 has a control terminal C by which telephone interface unit 128 can be controlled to establish communication over the telephone system.
- transceiver 124 receives audio signals, conveyed by the telephone system via telephone interface unit 128 and amplified by audio processor unit 126, for transmission to handunits 100 and 150.
- transceiver 124 receives "transmit data" (i.e., Txdata) from controller 132, for transmission to handunit 100.
- Base unit 120 also includes an AC power supply unit 136 for supplying operating power to the circuitry of the base unit.
- FIGURE 2 is a more detailed block diagram of duplex dual radio transceiver 124 of FIGURE 1.
- Antenna 122 is coupled to an RF amplifier 202 via a duplexer 200, which may be a type DPX 46/49-B10 duplexer manufactured by Soshin Electric Ltd..
- Handsets 100 and 150 transmit on different frequencies near 49 MHz.
- the signals received from the handunits are applied to mixers 205 and 235.
- Mixer 205 has a second input coupled to a local oscillator 210 for receiving an oscillator signal near 39 MHz. That is local oscillator 210 is tuned to oscillate at the difference frequency between the transmission frequency of one of the remote handunits and the first intermediate (IF) frequency of 10.72 MHz of receiver channel A.
- local oscillator 240 is tuned to oscillate at the difference between the transmission frequency of the other of the two remote handunits and the first nominal IF frequency of 10.68 MHz of receiver channel B.
- the respective first IF frequencies of channels A and B are offset from the nominal value of 10.7 MHz as explained in copending patent application bearing attorney docket number RCA 86,683.
- the down-converted 455 kHz signal of each channel is applied to respective IF amplifiers 230 and 260. After amplification the signals are detected and expanded in detector and expander units 232 and 262 to produce baseband audio signals. The baseband audio signals are then summed in a summer unit 265 and coupled to the telephone line via a hybrid transformer unit 270.
- A+B sidetone signal (i.e., a portion of the received signals from both channels) is coupled from hybrid transformer unit 270 via an automatic level control unit 275 to the transmitter side of the transceiver for transmission to the handunits.
- the sidetone signal corresponding to signals received from handset A is coupled back to handset A, and the signal received from handset A is also transmitted to handset B for A-to-B communication.
- the sidetone signal corresponding to signals received from handset B is coupled back to handset B and the signal received from handset B is also transmitted to handset A for B-to-A communication.
- the signal from automatic level control unit 275 is applied to the inputs of two compressor units 280 and 282.
- the compressed audio signals are applied to control inputs of separate oscillators 284 and 286 to modulate their respective output signals.
- Voltage-controlled crystal oscillators 284 and 286 oscillate at different frequencies near 15 MHz.
- the modulated signals are then applied to respective frequency triplers 288 and 290 to bring their final frequencies to different frequencies near 46 MHz.
- Frequency triplers 288 and 290 include a transistor and filter elements. Due to nonlinearities in the transistor, a third harmonic of the fundamental 15 MHz signal is formed.
- the filter elements are tuned to pass a narrow band of signals around the third harmonic (i.e., near 46 MHz) and block all others.
- the signals are then amplified in amplifiers 292 and 294, are combined, and applied via duplexer 200 to antenna 122.
Abstract
Description
- This invention concerns the field of cordless telephone instruments.
- This application is related to applications bearing attorney docket numbers RCA 86,682 and RCA 86,683 filed herewith.
- Cordless telephone instruments for use in the home are widely available. Such systems, comprise a base unit and a remote handunit. The base unit is coupled to the telephone line and communicates with the remote handunit via FM radio signals. With such a cordless telephone system a user can remove the handunit from its cradle and carry it with him a short distance from his house yet still be able to make and receive telephone calls. Such a cordless telephone set is known from GE cordless telephone model number 2-9675 manufactured by Thomson Consumer Electronics, Inc. Indianapolis, Indiana.
- If the user is engaged in a conversation via a cordless telephone, and a third person within the user's house wishes to join in the telephone conversation, that person can simply pick up a "hard-wired" extension telephone. Unfortunately, the third person cannot maintain participation in the conversation without remaining in the immediate area of the hard-wired telephone unit.
- A copending patent application bearing attorney docket number RCA 86,682 discloses a cordless telephone system which comprises a base unit and two handunits. In that system, a base unit transmits simultaneously to both handunits via two transmitter channels coupled to the same antenna, but during development of that system it was discovered that phase-locked loop (PLL) up-conversion used in the above-mentioned GE cordless telephone model number 2-9675 caused unacceptable intermodulation distortion in the transmitter signal from the base unit when the outputs of the transmitters were coupled together.
- It is herein recognized that in a cordless telephone system including a single base unit and at least two remote handunits, wherein the base unit employs two transmitter channels coupled to a single antenna, that the transmitter channels should include voltage controlled crystal oscillators (VCXOs) and frequency tripler circuitry, rather than PLLs in order to keep intermodulation distortion at the outputs of the transmitter amplifiers to a minimum.
- FIGURE 1 is a block diagram of a cordless telephone system according to the subject invention.
- FIGURE 2 is a more detailed block diagram of the base unit of FIGURE 1.
- FIGURE 3 shows representations of the transmitter spectrum observed for both PLL and VCXO operation.
- FIGURE 1 is a simplified illustration of a cordless telephone set comprising a
first handset unit 100, asecond handset unit 150, and abase unit 120. Becausehandset units handset 100 will be described.Handset unit 100 receives and transmits RF signals via anantenna 102.Antenna 102 is coupled to a duplexradio transceiver unit 104 which is capable of operation in a receiver mode and in a transmitter mode. In the receiver mode,transceiver unit 104 applies received and demodulated audio signals to anaudio processor unit 106 for amplification and ultimate reproduction inspeaker 108. Also in the receiver mode,transceiver 104 also provides digital data to the "receive data" (i.e., Rxdata) terminal of controller 112 In the transmitter mode,transceiver 104 receives audio signals, picked-up (i.e., detected) bymicrophone 110 and amplified byaudio processor unit 106, for transmission tobase unit 120. Also in transmitter mode,transceiver 104 receives "transmit data" (i.e., Txdata) from controller 112, for transmission tobase unit 120. Controller 112 is coupled to akeyboard 114 for receiving keystroke commands from a user. Handunit 100 also includes a power supply andcharging unit 116 for supplying operating power to the circuitry of the handunit. -
Base unit 120 receives and transmits RF signals via anantenna 122 toremote handunits Antenna 122 is coupled to a duplex dualradio transceiver unit 124 which is capable of operation in a receiver mode and in a transmitter mode. In the receiver mode,transceiver unit 124 receives RF signals at two different frequencies fromremote handunits audio processor unit 126 for amplification and coupling to the telephone system via atelephone interface unit 128.Telephone interface unit 128 is connected to the telephone system via two terminals traditionally known as tip (T) and ring (R). Also in the receiver mode,transceiver 124 also provides digital data to the "receive data" (i.e., Rxdata) terminal ofcontroller 132.Controller 132 has a control terminal C by whichtelephone interface unit 128 can be controlled to establish communication over the telephone system. In the transmitter mode,transceiver 124 receives audio signals, conveyed by the telephone system viatelephone interface unit 128 and amplified byaudio processor unit 126, for transmission tohandunits transceiver 124 receives "transmit data" (i.e., Txdata) fromcontroller 132, for transmission to handunit 100.Base unit 120 also includes an ACpower supply unit 136 for supplying operating power to the circuitry of the base unit. - FIGURE 2 is a more detailed block diagram of duplex
dual radio transceiver 124 of FIGURE 1.Antenna 122 is coupled to anRF amplifier 202 via aduplexer 200, which may be atype DPX 46/49-B10 duplexer manufactured by Soshin Electric Ltd..Handsets mixers local oscillator 210 for receiving an oscillator signal near 39 MHz. That islocal oscillator 210 is tuned to oscillate at the difference frequency between the transmission frequency of one of the remote handunits and the first intermediate (IF) frequency of 10.72 MHz of receiver channel A. Similarly,local oscillator 240 is tuned to oscillate at the difference between the transmission frequency of the other of the two remote handunits and the first nominal IF frequency of 10.68 MHz of receiver channel B. - The respective first IF frequencies of channels A and B are offset from the nominal value of 10.7 MHz as explained in copending patent application bearing attorney docket number RCA 86,683.
- The down-converted 455 kHz signal of each channel is applied to
respective IF amplifiers units summer unit 265 and coupled to the telephone line via ahybrid transformer unit 270. - For purposes of explanation, assume that handset A transmits the signal processed in receiver channel A and handset B transmits the signal processed in receiver channel B. An A+B sidetone signal (i.e., a portion of the received signals from both channels) is coupled from
hybrid transformer unit 270 via an automaticlevel control unit 275 to the transmitter side of the transceiver for transmission to the handunits. In this way, the sidetone signal corresponding to signals received from handset A is coupled back to handset A, and the signal received from handset A is also transmitted to handset B for A-to-B communication. Further, the sidetone signal corresponding to signals received from handset B is coupled back to handset B and the signal received from handset B is also transmitted to handset A for B-to-A communication. - The signal from automatic
level control unit 275 is applied to the inputs of twocompressor units separate oscillators crystal oscillators respective frequency triplers Frequency triplers amplifiers duplexer 200 toantenna 122. - As noted above, an early version of the subject apparatus employed a PLL up-converter unit in each transmitter channel. PLLs have been used recently because of the ease with which each of the 10 available cordless telephone channels can be synthesized. Some IMD (intermodulation distortion) was expected because of the configuration used, in which the output terminals of
output RF amplifiers amplifiers RF amplifiers
Claims (3)
- A cordless telephone set, comprising:
a first handunit (100); and
a base unit (120) and characterized by
a second handunit (150);
said base unit coupling signals of said handunits to a telephone system (TIP,RING);
wherein said handunits (100,150) and said base unit (120) communicate via a single antenna (122) mounted on said base unit;
said first handunit transmitting on a first frequency and receiving on a second frequency, said second handunit transmitting on a third frequency and receiving on a fourth frequency;
wherein said base unit comprises first and second transmitter channels transmitting at said second and fourth frequencies respectively, and output terminals of said first and second transmitter channels are coupled together through a low impedance;
said transmitter channels each including a voltage controlled crystal oscillator (284,286) and frequency tripler arrangement (288,290). - The cordless telephone set of claim 1, characterized in that,
audio signals to be transmitted by said base unit to said first (100) and second (150) handunits are coupled to a control input of said voltage controlled crystal oscillator (284,286) in each of said first and second transmitter channels for modulating the frequency of the output signal of each of said voltage controlled crystal oscillators. - The cordless telephone set of claim 1, characterized in that,
said modulated output signal of said voltage controlled crystal oscillator (284,286) in each of said first and second transmitter channels is applied to an input of said frequency tripler arrangement (288,290) in each of said transmitter channels, each of said frequency tripler arrangements being tuned to generate and select the third harmonic of said modulated output signal.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US81793392A | 1992-01-08 | 1992-01-08 | |
US817933 | 1992-01-08 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0550912A2 true EP0550912A2 (en) | 1993-07-14 |
EP0550912A3 EP0550912A3 (en) | 1993-08-11 |
EP0550912B1 EP0550912B1 (en) | 1998-09-16 |
Family
ID=25224240
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP92122128A Expired - Lifetime EP0550912B1 (en) | 1992-01-08 | 1992-12-30 | Use of a voltage controlled crystal oscillator in the base unit of a two-handset cordless telephone system |
Country Status (10)
Country | Link |
---|---|
US (1) | US5625674A (en) |
EP (1) | EP0550912B1 (en) |
JP (1) | JP2750492B2 (en) |
KR (1) | KR970006042B1 (en) |
CN (1) | CN1028702C (en) |
CA (1) | CA2085722C (en) |
DE (1) | DE69227017T2 (en) |
MX (1) | MX9300048A (en) |
MY (1) | MY108906A (en) |
SG (1) | SG84476A1 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BR9506894B1 (en) * | 1994-02-24 | 2010-08-10 | method of operating a cellular telecommunications system, method of activating a cellular mobile station and a mobile station in a radio cellular telecommunications system. | |
US6011959A (en) * | 1998-03-17 | 2000-01-04 | Motorola, Inc. | Combiner circuit for dual band voltage controlled oscillators |
US6298221B1 (en) * | 1998-04-01 | 2001-10-02 | Denso Corporation | Adaptive receiver linearity techniques for a radio transceiver |
US6169912B1 (en) | 1999-03-31 | 2001-01-02 | Pericom Semiconductor Corp. | RF front-end with signal cancellation using receiver signal to eliminate duplexer for a cordless phone |
WO2010036890A1 (en) * | 2008-09-26 | 2010-04-01 | Superior Modular Products Incorporated | Communications system ans apparatus for providing wireless communications within a building |
Citations (5)
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DE2615769A1 (en) * | 1976-04-10 | 1977-10-27 | Securiton Ag | SECURITY ALARM SYSTEM FOR TRANSMISSION OF CODED SIGNALS, WITH A TRANSMITTER DISCOVERED BY A PERSONAL PORTABLE TRANSMITTER |
US4134085A (en) * | 1977-05-31 | 1979-01-09 | Driscoll Michael M | Narrow deviation voltage controlled crystal oscillator for mobile radio |
EP0203819A2 (en) * | 1985-05-30 | 1986-12-03 | Nec Corporation | Cordless telephone system |
EP0304998A2 (en) * | 1987-08-26 | 1989-03-01 | Koninklijke Philips Electronics N.V. | PABX cordless telephone system |
US4935927A (en) * | 1987-11-20 | 1990-06-19 | International Mobile Machines Corporation | Base station emulator |
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DE1022275B (en) * | 1953-11-14 | 1958-01-09 | Siemens Elektrogeraete Gmbh | Method and device for receiving sound transmissions stereophonically transmitted via separate modulated carrier waves |
DE2149514A1 (en) * | 1971-10-04 | 1973-04-12 | Siemens Ag | CIRCUIT ARRANGEMENT FOR SIMULTANEOUS AND UNDISTURBED RECEPTION OF MULTIPLE TRANSMITTERS WITH A SINGLE RECEIVER |
JPS5411606A (en) * | 1977-06-27 | 1979-01-27 | Fujitsu Ltd | Radio communication system |
US4476575A (en) * | 1982-12-13 | 1984-10-09 | General Electric Company | Radio transceiver |
US4741019A (en) * | 1984-03-15 | 1988-04-26 | Sanyo Electric Co., Ltd. | Cordless telephone |
JPS62243432A (en) * | 1986-04-16 | 1987-10-23 | Matsushita Electric Works Ltd | Radio transmission and reception system |
JPH0815354B2 (en) * | 1986-10-30 | 1996-02-14 | 日本電気株式会社 | Wireless telephone equipment |
US4759078A (en) * | 1986-11-14 | 1988-07-19 | Rose Communication Systems, Inc. | Coordinated local oscillator receiving system |
JPH0744485B2 (en) * | 1987-05-22 | 1995-05-15 | 三菱電機株式会社 | Car phone equipment |
US4891637A (en) * | 1988-01-07 | 1990-01-02 | Motorola, Inc. | Acknowledge back pager with apparatus for controlling transmit frequency |
AT390702B (en) * | 1988-05-20 | 1990-06-25 | Siemens Ag Oesterreich | CORDLESS TELEPHONE DEVICE |
JPH02291732A (en) * | 1989-05-01 | 1990-12-03 | Iwatsu Electric Co Ltd | Dispersed reception system for mobile communication system |
US5133002A (en) * | 1989-07-28 | 1992-07-21 | Ascii Corporation | Radiotelephone system that maintains synchronization between base and subordinate units while shifting carrier frequencies |
JPH047923A (en) * | 1990-04-25 | 1992-01-13 | Sharp Corp | Cordless telephone set |
US5239686A (en) * | 1991-04-29 | 1993-08-24 | Echelon Corporation | Transceiver with rapid mode switching capability |
-
1992
- 1992-12-17 CA CA002085722A patent/CA2085722C/en not_active Expired - Fee Related
- 1992-12-30 EP EP92122128A patent/EP0550912B1/en not_active Expired - Lifetime
- 1992-12-30 DE DE69227017T patent/DE69227017T2/en not_active Expired - Fee Related
- 1992-12-30 SG SG9602417A patent/SG84476A1/en unknown
-
1993
- 1993-01-04 MY MYPI93000001A patent/MY108906A/en unknown
- 1993-01-05 KR KR1019930000034A patent/KR970006042B1/en not_active IP Right Cessation
- 1993-01-07 CN CN93100109A patent/CN1028702C/en not_active Expired - Fee Related
- 1993-01-07 MX MX9300048A patent/MX9300048A/en not_active IP Right Cessation
- 1993-01-07 JP JP5018110A patent/JP2750492B2/en not_active Expired - Fee Related
-
1996
- 1996-07-22 US US08/681,132 patent/US5625674A/en not_active Expired - Lifetime
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2615769A1 (en) * | 1976-04-10 | 1977-10-27 | Securiton Ag | SECURITY ALARM SYSTEM FOR TRANSMISSION OF CODED SIGNALS, WITH A TRANSMITTER DISCOVERED BY A PERSONAL PORTABLE TRANSMITTER |
US4134085A (en) * | 1977-05-31 | 1979-01-09 | Driscoll Michael M | Narrow deviation voltage controlled crystal oscillator for mobile radio |
EP0203819A2 (en) * | 1985-05-30 | 1986-12-03 | Nec Corporation | Cordless telephone system |
EP0304998A2 (en) * | 1987-08-26 | 1989-03-01 | Koninklijke Philips Electronics N.V. | PABX cordless telephone system |
US4935927A (en) * | 1987-11-20 | 1990-06-19 | International Mobile Machines Corporation | Base station emulator |
Also Published As
Publication number | Publication date |
---|---|
US5625674A (en) | 1997-04-29 |
JPH05268113A (en) | 1993-10-15 |
MX9300048A (en) | 1993-07-01 |
DE69227017D1 (en) | 1998-10-22 |
CN1077576A (en) | 1993-10-20 |
CA2085722A1 (en) | 1993-07-09 |
EP0550912A3 (en) | 1993-08-11 |
EP0550912B1 (en) | 1998-09-16 |
KR930017358A (en) | 1993-08-30 |
KR970006042B1 (en) | 1997-04-23 |
DE69227017T2 (en) | 1999-04-15 |
MY108906A (en) | 1996-11-30 |
SG84476A1 (en) | 2001-11-20 |
CA2085722C (en) | 1997-02-25 |
JP2750492B2 (en) | 1998-05-13 |
CN1028702C (en) | 1995-05-31 |
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